In a wireless communication system, a transmitting device transmits a signal through a radio frequency channel. If signal quality is deteriorated due to occurrence of an obstacle to the radio channel formed between the transmitting device and a receiving device which is a destination of the signal, the signal may not successfully reach the receiving device or, even if the signal reaches the receiving device, the signal may not be correctly demodulated or decoded due to errors.
FIG. 1 is a diagram for explaining an example of low reception signal strength. Particularly, FIG. 1 illustrates an example of increasing pathloss between an evolved NodeB (eNB) and a user equipment (UE). When a UE, UE1 for example, is located at a cell edge of a geographic region served by an eNB or when an obstacle such as a building is positioned between an eNB and a UE, UE2 for example, so that a signal transmission path is blocked, a signal from the UE to the eNB or from the eNB to the UE may not correctly be transmitted.